1. Field of the Invention
The present invention relates to an angle sensor, especially a steering angle sensor for detecting a steering angle of a rotor such as a steering of a vehicle.
2. Description of the Related Art
With a vehicular steering shaft of the related art, an absolute steering angle sensor or a relative steering angle sensor has heretofore been used as a steering angle sensor available to detect a steering angle of a rotor.
The absolute steering angle sensor of the related art is comprised of a first gear rotatable in connection with a steering shaft, a second gear in mesh with the first gear, and a third gear. A gear ratio (a ratio in a number of teeth) of the second gear to the first gear differs from a gear ratio of the third gear to the first gear. In order to measure rotation angles of the second and third gears, magnetic sensors measure rotation angles of magnets mounted to the second and third gears, respectively. The rotation angles of the first gear and the steering shaft can be obtained depending upon the rotation angles of the second and third gears.
Further, a relative steering angle sensor described in Japanese Patent Provisional Publication No. 2000-180113 has heretofore been known in the art.
Technology disclosed in Japanese Patent Provisional Publication No. 2000-180113 includes a multiple-pole magnetized ring with an N-pole and S-pole being alternately located along a circumferential periphery. A magnetic reluctance element detects variation in a magnetic field occurring during rotation of the magnetized ring, thereby producing an A-phase pulse (a first pulse) and a B-phase pulse (a second pulse) resulting from fluctuation in the magnetic field. Additionally, a monopole-magnetized portion is provided on one area of the circumferential periphery. A hole-effect IC detects the monopole-magnetized portion, thereby producing a Z-phase pulse (a third pulse).
Depending upon the three-phase (A-, B- and Z-phases) pulse signals described above, a rotation angle, a rotation direction and a reference position of the steering shaft are detected. As a result, a steering angle of the steering shaft is measured.
That is, with a host system applied with the three-phase pulse signals, the rotation angle and rotation direction are detected in accordance with the A-phase pulse and B-phase pulse. Additionally, depending upon the Z-phase pulse, a neutral position (a position at which the steering shaft is oriented in a straight-running direction) is detected.
However, the relative steering angle sensors of the related art are formed in different structures depending upon specifications such as resolutions (minimal steering angles that can be detected) of detected steering angles. That is, depending upon the specifications, the magnetized rings are different in size and have different number of magnetized poles while the magnetic sensors must be mounted in different positions, resulting in non-standardized status. For this reason, no component parts are commoditized and thus, a need arises for preparing different component parts.
Further, with the absolute steering angle sensor and the relative steering angle sensor, packages (storage cases) and detecting structures (including magnetic sensors and magnets) are not commoditized. This results in a need for preparing different packages and detecting structures, resulting in an issue with an increase in the number of component parts.
The present invention aims to address such a related art issue and has an object to provide a steering angle sensor by which component parts can be standardized. As a result, the present invention is able to properly comply with various situations depending upon specifications.